1. Field of the Invention
The present invention relates to the exercise of control over the operation of a furnace and particularly to the collection of gas samples at various locations within a furnace and the measurement of the temperature at each gas sampling point. More specifically, this invention is directed to a sampling probe for insertion into a furnace and especially to a probe for simultaneously taking multiple gas samples and measuring the temperature at each sampling point. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
In order for a blast furnace, particularly a modern furnace which operates with a comparatively high pressure, to be operated so as to obtain the optimum results, it is essential to monitor conditions within the furnace. The conditions which are desirably monitored include the chemical composition of the gases produced and the temperature profile across the furnace charge. These conditions have previously been sensed through the use of probes which may be inserted into the furnace, both above and into the charge, to collect gas samples and take temperature measurements. The sampling must, of course, be performed at a sufficient number of locations so as to enable the plotting of curves which are commensurate with the furnace operation. It is these curves which provide the furnace operator with the information necessary for control purposes.
There are two types of sampling probes generally known in the prior art. Firstly, there are probes which are fixed in position above the surface of the furnace charge. Secondly, there are probes which are periodically inserted through the wall of the furnace into the mass of the charge. Examples of probes of the latter type may be seen from U.S. Pat. Nos. 3,888,123 and 4,044,612. Those prior art probes which are inserted into the charge itself are typically associated with an external vibrator since a vibrating probe will penetrate the furnace charge with less difficulty.
In order for a furnace probe to perform its intended function, it is essential that the measurements taken with the probe be accurate and reproducible. Unfortunately, such accurate and reproducible measurements have not been insured by the prior art probes, this being particularly true in the case of temperature measurements which were obtained through the use of thermocouples.
Applicants have discovered that the temperature measurement inaccuracies associated with prior art furnace probes may, to a large degree, be attributed to the manner in which the thermocouples were installed in the probes. A typical probe will have a plurality of gas sampling orifices distributed along its length and there will be a thermocouple positioned within the probe and juxtapositioned to each sampling orifice. Due to manufacturing tolerances and assembly errors, and particularly because of the fact that the probe will be subjected to vibration and will undergo thermally induced expansion and subsequent contraction, the thermocouples do not all occupy and/or remain in the same relative position with respect to their associated gas admission orifices. A relative displacement of only a few millimeters is sufficient to produce significant inaccuracies in the temperature measurement. Bearing in mind that the temperature measurements are employed to plot a profile, inaccurate measurements make it impossible to produce a curve which will be representative of the temperature. The inability to accurately produce a temperature profile, in turn, greatly reduces the utility of the probe.
Furnace probes of the type being described must, in addition to providing accurate measurement, be of comparatively modest cost and be characterized by ease of initial assembly and subsequent repair. These requirements are dictated by the demanding environment in which the probes are used, this environment resulting in the need to frequently replace or repair the device. Thus, economic considerations dictate that a furnace gas/temperature probe be easy to assemble and install and that its initial cost be minimized.